The human gastrointestinal tract is a system by which ingested food is digested and absorbed in order to provide the body with essential nutrients. The human gastrointestinal tract includes the small intestine, which is the longest portion of the digestive tract. The small intestine has three sections: the duodenum, jejunum and ileum. The duodenum, where most chemical digestion takes place, precedes the jejunum and ileum and is the shortest part (typically 25-30 cm in length) of the small intestine. The duodenum begins with the duodenal bulb and ends at the ligament of Treitz.
The digestion process is regulated by several hormones, some of which are released by the gastrointestinal tract. Additionally, many digestive enzymes are secreted by the gastrointestinal tract and the pancreas to aid in the digestion of food. Other endogenous secretions, such as bile, facilitate the digestion of lipids in the small intestine. Bile is typically stored in the gallbladder and upon eating is discharged into the duodenum.
Obesity and type II diabetes are serious health concerns. It is believed that obesity promotes insulin resistance, and has been found to play an important role in the pathogenesis of diabetes. Accordingly, weight loss is generally recommended, in order to lower elevated blood glucose levels in overweight and obese individuals with type II diabetes.
Some weight loss surgical techniques currently include several types of bariatric surgical procedures, including malabsorptive procedures, e.g., biliopancreatic diversion and biliopancreatic diversion with a duodenal switch. Generally, these diversion procedures, although they also reduce stomach size, are based mainly on creating malabsorption by bypassing digestion in the duodenum and other parts of the small intestine.